The 31-year-old midfielder was originally ruled out until the New Year after undergoing knee surgery in the summer.
But Sunderland boss David Moyes has revealed Larsson, along with Vito Mannone, is back in full training with the rest of the squad, and Moyes has hailed his “incredible return”.
Larsson will not be ready for competitive action for at least a month, though, as he needs to build up his fitness levels and Moyes is wary of rushing him back too soon.
Moyes will look to involve the experienced Swede in some of the club’s Under-23 fixtures over the coming weeks.
The Sunderland boss has praised his determination and desire and that of Sunderland’s other injured players as they look to get back playing sooner than originally anticipated.
“Seb has dipped in and out a little bit but started full training on Monday,” said Moyes.
“I think Seb will need the best part of three to four weeks on football sessions and what not and hopefully we might get him a couple of Under-23 games in the process.
“Hopefully it is quicker. But he has done really well.
“I don’t want to risk his injury too soon.
“It is an incredible return.”
There was further good news regarding Mannone too, with the Italian goalkeeper back training.
Mannone has been out since the end of August with an elbow injury suffered at the end of a training session, with the impressive Jordan Pickford replacing him in the Sunderland side.
Fabio Borini (adductor) and Lee Cattermole (back) have been running at the Academy of Light but there is no timescale for their return.
“Seb and Vito have come back much quicker,” added Moyes.
“Vito has been doing an awful lot of goalkeeping work and diving. He is not far away.
“Borini has been running too so there are just signs that these boys are coming back and maybe getting closer to being ready.
“I think it as much down to their determination. They have shown great desire to get back quickly.
“Most of them are all back quicker than we originally thought.”